TreeDamageAlert No 120

7th Sept

2007

AAIS Alice Holt Lodge Wrecclesham  Farnham  Surrey GU10 4LH

Call the Tree Helpline on: 09065 161147

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Have you noticed …..?

Tree care and management rely on observation. ‘Visual Tree Assessment’ is probably the most obvious instance of attention being paid to the detail of trees. No matter how good the system of tree inspection adopted it has little value if key features are unnoticed or if they are not interpreted.

Diagnosis of the cause(s) of ill-health in a tree depends upon observation of symptoms and details often in comparison with other known examples of the same species or variety. Many of these are small details that have been noticed by a person but they are unrecorded in the literature because there is no corroborative evidence. Nevertheless, to the individual observer they are invaluable and part of both their accumulation of knowledge and continuing professional development. Knowledge and practice in arboriculture are dependent upon individuals observing details and sharing their experiences with others in the industry. Sometimes scientific investigation and research may follow to confirm the interpretation. However, when dealing with mature trees statistically meaningful results are difficult to obtain, if not impossible to achieve because there are so many variables.

The weather in the summer of 2007 has been unusual even by comparison with the immediately previous years. Many trees and shrubs flushed and flowered early, up to three weeks in some cases, others, like Ash, were very late flushing (TDA 117). What will be the effect for the future?

Have you noticed specimens of Robinia pseudoacacia ‘Frisia’ shedding most of the leaflets but the rachis (the central axis of a pinnately compound leaf) remains? This suggests that abscission has not occurred. In contrast the species R. pseudoacacia appear to be retaining their leaves. The reason for this is not understood.

Another observation relates to Beeches (Fagus sylvatica) with purple foliage – no specific cultivar appears to be involved. It is common to find that leaves within the crown have less colouring than those on the outside of the crown. In fact the inner leaves often look distinctly green. This summer, however, mature trees have had areas of foliage visible on the outer crown with a greener than usual appearance. That is a subjective observation because of a dearth of information about the cultivars being observed, and no data on the actual shade of colour in previous summers.

What is the cause of this phenomenon which appears to be confined to Beech, if the observations are correct? One suggestion relates to the general lack of bright sunlight during the exceptionally wet late spring and early summer. If that is the case would the leaves become darker when they finally received direct sunlight? This appears to have not been the case with the greeny purple foliage persisting.

Keep your eyes open and share your observations with colleagues!

Derek PatchArboricultural Advisory and Information Service, Farnham.

This is one of an occasional series of Tree Damage Alerts produced for the benefit of the arboricultural profession and issued by the Arboricultural Advisory and Information Service.